WO2023115571A1 - 测量距离的方法及激光雷达 - Google Patents

测量距离的方法及激光雷达 Download PDF

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Publication number
WO2023115571A1
WO2023115571A1 PCT/CN2021/141346 CN2021141346W WO2023115571A1 WO 2023115571 A1 WO2023115571 A1 WO 2023115571A1 CN 2021141346 W CN2021141346 W CN 2021141346W WO 2023115571 A1 WO2023115571 A1 WO 2023115571A1
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Prior art keywords
echo
distance
target
laser
moment
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PCT/CN2021/141346
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English (en)
French (fr)
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李洪鹏
郑睿童
王世玮
沈罗丰
张正杰
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探维科技(北京)有限公司
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Publication of WO2023115571A1 publication Critical patent/WO2023115571A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S17/36—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated with phase comparison between the received signal and the contemporaneously transmitted signal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/46—Indirect determination of position data
    • G01S17/48—Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves

Definitions

  • the present application relates to the technical field of laser detection, in particular to a method for measuring distance and laser radar.
  • the equipment used to measure the distance includes laser radar (Laser Radar), which is classified according to the type of laser emitted by the laser radar.
  • the laser radar can be divided into pulse laser radar, continuous laser radar and so on.
  • the pulsed laser radar emits laser pulses
  • the laser pulses are reflected by the object to be measured to generate echoes
  • the pulsed laser radar receives the echoes.
  • the difference between the reception time of the echo and the emission time of the laser pulse is calculated to obtain the time-of-flight of the laser pulse. From the time-of-flight and the flight speed of the laser pulse, the distance to the object can be calculated.
  • the method provided by the related art has a certain ranging blind area.
  • the reason is that the laser pulse emitted by the laser pulse is not only reflected by the object to be measured to generate echoes, but also reflected by the inner and outer structures of the lidar itself to generate clutter.
  • the energy of the clutter is greater than that of the echo. Therefore, if the lidar receives an echo during the process of receiving clutter, the echo received by the lidar will be overwhelmed by the more energetic clutter, or the lidar cannot recognize the received echo.
  • the laser radar cannot determine the receiving time of the echo, and thus cannot calculate the distance of the object, thus forming a ranging blind zone. It is precisely because the method provided by the related technology has a certain distance measurement blind area, so the distance measurement range is limited, and the applicability is not strong.
  • the embodiment of the present application provides a method for measuring distance and a laser radar to solve the problem that the distance measurement range is limited and the applicability of the method provided by the related art is not strong. Described technical scheme is as follows:
  • a method for measuring distance is provided, the method is applied to a chip included in the laser radar, and the laser radar also includes a first laser emitter connected to the chip, a second laser emitter and a laser detector, the method includes:
  • the target echo includes at least one of a first echo and a second echo
  • the first echo is an echo formed by reflecting the first laser pulse from the target object
  • the second echo is formed by reflecting the second laser pulse on the target object echoes
  • the target time includes at least one of the first time and the second time.
  • determining the target distance to the target object based on the time when the target echo is received and the target time includes: determining the reference distance to the target object according to the time when the target echo is received and the target time Distance: Determines the target distance to the target object based on the reference distance to the target object.
  • the target echo includes the first echo and the second echo
  • the target time includes the first time and the second time
  • determine the distance between The reference distance including: determining the first distance according to the moment of receiving the first echo and the first moment, determining the second distance according to the moment of receiving the second echo and the second moment; according to the first distance and the second distance Determine the reference distance to the target object, the reference distance is greater than the first distance threshold and smaller than the second distance threshold, the first distance threshold is based on the lower limit of the first distance measurement range, and the second distance threshold is the upper limit of the second distance measurement range , the energy of the first laser pulse is greater than the energy of the second laser pulse.
  • determining the target distance to the target object based on the reference distance to the target object includes: detecting a first sub-moment when the amplitude of the rising edge of the first echo reaches the reference amplitude, And the amplitude of the rising edge of the second echo reaches the second sub-moment of the reference amplitude; the difference between the first sub-moment and the second sub-moment is determined as the correction index value, and the calibration information is queried to obtain the correction index value corresponding to The distance compensation value; according to the reference distance and the distance compensation value, determine the target distance to the target object.
  • the target echo is the first echo
  • the target time is the first time
  • determining the reference distance to the target object includes: according to the received The time of the first echo and the first time determine the reference distance to the target object, the reference distance is greater than the second distance threshold and less than the third distance threshold, the second distance threshold is the upper limit of the second ranging range, and the third distance The threshold is the upper limit of the first ranging range, and the energy of the first laser pulse is greater than the energy of the second laser pulse.
  • the target echo is the second echo
  • the target time is the second time
  • determining the reference distance to the target object includes: according to the received The time of the second echo and the second time determine the reference distance to the target object, the reference distance is greater than the fourth distance threshold and less than the first distance threshold, the first distance threshold is the lower limit of the first distance measurement range, and the fourth distance The threshold is based on the lower limit of the second ranging range, and the energy of the first laser pulse is greater than the energy of the second laser pulse.
  • the time difference between the first moment and the second moment is determined based on at least one of the scanning frequency of the laser radar and the included angle of the pointing angle, and the included angle of the pointing angle is the pointing angle of the first laser emitter angle and the pointing angle of the second laser emitter.
  • the time difference is smaller than the upper limit of the time difference
  • the upper limit of the time difference is the difference between the light emitting period of the first laser pulse and the pulse width of the first laser pulse
  • the light emitting period of the first laser pulse is based on the laser radar At least one of the scanning frequency, the horizontal field of view of the laser radar, and the horizontal resolution of the laser radar is determined.
  • the time difference is greater than the lower limit of the time difference, which is the pulse width of the first laser pulse, the recovery time of the laser detector, and the time required to measure the upper limit of the first ranging range maximum value.
  • lidar comprises a first laser emitter, a second laser emitter, a laser detector and a chip, and the first laser emitter, the second laser emitter, and the laser detector are respectively connected to the chip , the chip is configured to execute the method for measuring distance provided by any exemplary embodiment of the present application.
  • a device for measuring distance is provided, the device is applied to a chip included in the laser radar, and the laser radar also includes a first laser emitter, a second laser emitter and a laser detector connected to the chip, and the device includes:
  • the control module is used to control the first laser emitter to emit the first laser pulse for the target object at the first moment, and control the second laser emitter to emit the second laser pulse for the target object at the second moment, the first moment is earlier than the second At any moment, the energy of the first laser pulse is different from the energy of the second laser pulse, the first laser pulse corresponds to the first ranging range, and the second laser pulse corresponds to the second ranging range;
  • the control module is also used to control the laser detector to receive the target echo
  • a determining module configured to determine the target distance to the target object based on the time when the target echo is received and the target time, the target distance is located in the union of the first ranging range and the second ranging range, and the target echo includes At least one of the first echo and the second echo, the first echo is the echo formed by reflecting the first laser pulse from the target object, and the second echo is the echo formed by reflecting the second laser pulse from the target object,
  • the target time includes at least one of the first time and the second time.
  • the determining module is configured to determine the reference distance to the target object according to the time when the target echo is received and the target time; and determine the distance to the target object based on the reference distance to the target object. target distance.
  • the target echo includes a first echo and a second echo
  • the target moment includes a first moment and a second moment
  • the determining module is configured to, according to the moment when the first echo is received and the first moment Determine the first distance, determine the second distance according to the moment when the second echo is received and the second moment; determine the reference distance to the target object according to the first distance and the second distance, and the reference distance is greater than the first distance threshold and less than The second distance threshold
  • the first distance threshold is based on the lower limit of the first ranging range
  • the second distance threshold is the upper limit of the second ranging range
  • the energy of the first laser pulse is greater than the energy of the second laser pulse.
  • the determination module is configured to detect the first sub-moment when the amplitude of the rising edge of the first echo reaches the reference amplitude, and the second sub-moment when the amplitude of the rising edge of the second echo reaches the reference amplitude
  • the second sub-moment determine the difference between the first sub-moment and the second sub-moment as the correction index value, query the correction information to obtain the distance compensation value corresponding to the correction index value; determine the distance from the target object according to the reference distance and the distance compensation value distance between targets.
  • the target echo is the first echo
  • the target moment is the first moment
  • the determining module is configured to determine the reference distance to the target object according to the moment when the first echo is received and the first moment , the reference distance is greater than the second distance threshold and less than the third distance threshold, the second distance threshold is the upper limit of the second ranging range, the third distance threshold is the upper limit of the first ranging range, and the energy of the first laser pulse is greater than the second Energy of the laser pulse.
  • the target echo is the second echo
  • the target time is the second time
  • the determining module is configured to determine the reference distance to the target object according to the time when the second echo is received and the second time , the reference distance is greater than the fourth distance threshold and less than the first distance threshold, the first distance threshold is the lower limit of the first ranging range, the fourth distance threshold is based on the lower limit of the second ranging range, and the energy of the first laser pulse is greater than the first The energy of the second laser pulse.
  • the time difference between the first moment and the second moment is determined based on at least one of the scanning frequency of the laser radar and the included angle of the pointing angle, and the included angle of the pointing angle is the pointing angle of the first laser emitter angle and the pointing angle of the second laser emitter.
  • the time difference is smaller than the upper limit of the time difference
  • the upper limit of the time difference is the difference between the light emitting period of the first laser pulse and the pulse width of the first laser pulse
  • the light emitting period of the first laser pulse is based on the laser radar At least one of the scanning frequency, the horizontal field of view of the laser radar, and the horizontal resolution of the laser radar is determined.
  • the time difference is greater than the lower limit of the time difference, which is the pulse width of the first laser pulse, the recovery time of the laser detector, and the time required to measure the upper limit of the first ranging range maximum value.
  • the energy of the two laser pulses emitted by the two laser emitters included in the laser radar is different, so the ranging ranges corresponding to the two laser pulses are also different. Since the ranging range of the lidar is the union of the ranging ranges corresponding to the two laser pulses, the distance measuring range of the lidar is extended and the applicability of the lidar is improved.
  • Fig. 1 is a schematic diagram of a clutter and an echo provided by an embodiment of the present application
  • FIG. 2 is a schematic structural diagram of a lidar provided in an embodiment of the present application.
  • Fig. 3 is a schematic diagram of an electrical signal obtained by photoelectric conversion provided by an embodiment of the present application.
  • FIG. 4 is a schematic structural diagram of a lidar provided in an embodiment of the present application.
  • Fig. 5 is a schematic structural diagram of an optical component provided by an embodiment of the present application.
  • Fig. 6 is a schematic diagram of a horizontal field of view provided by an embodiment of the present application.
  • Fig. 7 is a schematic diagram of a first laser pulse and a second laser pulse irradiating to the same position provided by the embodiment of the present application;
  • Fig. 8 is a schematic diagram of a laser detector receiving the first echo and the second echo provided by the embodiment of the present application;
  • FIG. 9 is a flow chart of a method for measuring distance provided in an embodiment of the present application.
  • Fig. 10 is a schematic diagram of a first laser pulse and a second laser pulse provided by an embodiment of the present application.
  • Fig. 11 is a schematic diagram of a target echo in a different situation provided by the embodiment of the present application.
  • Fig. 12 is a schematic diagram of a target echo provided by an embodiment of the present application.
  • Fig. 13 is a schematic diagram of determining a correction index value provided by an embodiment of the present application.
  • Fig. 14 is a schematic diagram of determining a correction index value provided by an embodiment of the present application.
  • Fig. 15 is a schematic diagram of a target echo provided by an embodiment of the present application.
  • Fig. 16 is a schematic diagram of a target echo provided by an embodiment of the present application.
  • Fig. 17 is a schematic structural diagram of a device for measuring distance provided by an embodiment of the present application.
  • laser radar is a device used to measure distance
  • pulse laser radar is one of the laser radars.
  • related technologies provide a TOF method that calculates the distance to an object based on the time-of-flight (i.e., travel time) and flight speed (i.e., propagation speed) of laser pulses.
  • the time when the laser radar sends a laser pulse to the object is t 0
  • the time when the laser radar receives the echo (formed by the laser pulse reflected by the object) is t 1
  • the flying speed of the laser pulse is recorded as c, and the distance to the object is calculated according to the following formula (1):
  • this method has a certain ranging blind area, and the ranging blind area will be described below.
  • the lidar After the lidar emits laser pulses to the object, in addition to the object reflecting the laser pulse to form an echo, the inner and outer structures of the lidar will also reflect the laser pulse, thereby forming clutter, and the lidar will receive the formed clutter. Since the formation position of the clutter is relatively close to the laser radar, and the reflection of the inner and outer structures of the laser radar is close to the mirror reflection, the energy of the clutter is relatively large, so that the clutter has a large amplitude and pulse width. Referring to Fig. 1, Fig. 1 shows a clutter waveform, and the integrated value of the clutter waveform represents the energy of the clutter.
  • the clutter waveform is a saturated waveform, and since the actual maximum amplitude of the clutter exceeds the maximum amplitude that the lidar can receive, it appears as a saturated waveform.
  • the pulse width is the half-maximum width, and the half-maximum width is the waveform width at half the amplitude.
  • Fig. 1 shows an echo waveform, and the integrated value of the echo waveform represents the energy of the echo.
  • the echo waveform may be a saturated waveform or an unsaturated waveform, and the unsaturated waveform shown in FIG. 1 is only an example and is not used to limit the echo waveform.
  • the lidar Regardless of the echo waveform, if the lidar receives the echo during the process of receiving the clutter, the echo will be submerged by the clutter because the energy is smaller than the clutter, or the lidar cannot detect the clutter from the clutter. The echo is identified. Therefore, the lidar cannot determine the time at which the echo was received (ie t 1 above), and thus the distance of the object.
  • the laser radar in the process of receiving clutter, the laser radar cannot determine the distance of the object, so the distance range corresponding to the period of time when the laser radar receives the clutter is the ranging blind zone. Since the formation of clutter is relatively close to the laser radar, the laser radar will receive the clutter within a short period of time after the laser pulse is emitted. within a relatively short distance. That is to say, the above-mentioned ranging blind spots often exist at relatively short distances.
  • the ranging blind area is related to the materials of the inner and outer structures of the lidar, the optical power of the lidar (the optical power affects the energy of the laser pulse emitted by the lidar), and the detection gain of the lidar (the detection gain affects the received echoes and clutter sensitivity) and other factors.
  • the duration of receiving clutter is about 30 ns (unit: nanosecond).
  • the flight speed c of the above-mentioned laser pulse is taken as 3 ⁇ 10 8 m/s (unit: m/s)
  • the lidar comprises a first laser emitter 1, a second laser emitter 2, a laser detector 3 and a chip 4, and the first laser emitter 1, the second laser emitter 2, and the laser detector 3 are respectively connected with Chip 4 is connected.
  • the laser detector 3 is a linear array detector, such as an integrating photodetector such as an APD (Avalanche Photo Diode, avalanche photodiode).
  • the chip 4 sends a first electrical trigger signal to the first laser transmitter 1 , so that the first laser transmitter 1 emits a first laser pulse for a target object that needs to be measured according to the first electrical trigger signal. Moreover, the chip 4 records the moment when the first laser emitter 1 emits the first laser pulse as the first moment. The chip 4 also sends a second electrical trigger signal to the second laser transmitter 2, so that the second laser transmitter 2 emits a second laser pulse for the target object according to the second electrical trigger signal, and the chip 4 sends the second laser transmitter 2 The moment of the second laser pulse is recorded as the second moment.
  • the above-mentioned first laser pulse corresponds to a certain distance measurement range, that is, the first distance measurement range, and the first distance measurement range is related to the energy of the first laser pulse.
  • the greater the energy of the first laser pulse the greater the lower limit of the first ranging range, and the greater the upper limit of the first ranging range.
  • the lower limit of the first ranging range is also the maximum distance of the ranging blind area corresponding to the first laser pulse.
  • the laser detector 3 can receive the first echo formed by the first laser pulse reflected by the target object, and can determine the moment when the first echo is received. If the distance to the target object is less than the lower limit of the first ranging range, the first echo will be submerged by the first clutter corresponding to the first laser pulse, and even if the laser detector 3 receives the first echo, it will Unable to determine the moment the first echo was received.
  • the first laser pulse may not be able to fly to the target object due to insufficient energy, and the first echo cannot be formed, or the first laser pulse has already flown to the target object, but the first echo formed by the reflection of the target object cannot fly to the laser detector 3 due to insufficient energy.
  • the laser detector 3 cannot receive the first echo, and cannot determine the moment when the first echo is received. Therefore, the laser detector 3 may or may not receive the first echo.
  • the second laser beam emitted by the second laser transmitter 2 can be reflected by the target object to form a second echo, and the second echo also corresponds to a certain distance measurement range, that is, the second distance measurement range.
  • the range is related to the energy of the second laser pulse. The greater the energy of the second laser pulse, the greater the lower limit of the second ranging range, and the greater the upper limit of the second ranging range. Wherein, the lower limit of the second ranging range is also the maximum distance of the ranging blind area corresponding to the second laser pulse.
  • the laser detector 3 may or may not receive the second echo.
  • what the laser detector 3 can receive is at least one of the first echo and the second echo.
  • the at least one echo is referred to as a target echo for ease of description.
  • the laser detector 3 After receiving the target echo, the laser detector 3 performs photoelectric conversion on the target echo to obtain an electrical signal with a certain waveform. As shown in FIG. 3 , FIG. 3 shows an exemplary electrical signal, the abscissa of the electrical signal is time, and the ordinate is relative optical power.
  • the laser detector 3 sends the converted electrical signal to the chip 4, and the chip 4 determines the moment when the amplitude of the rising edge of the electrical signal reaches a certain amplitude as the moment when the target echo is received.
  • the time t2 shown in Fig. 3 is the time when the target echo is received.
  • the chip 4 After determining the time when the target echo is received, the chip 4 determines the target distance to the target object based on the time when the target echo is received and the target time.
  • the target moment includes at least one moment among the above-mentioned first moment and second moment.
  • the chip 4 includes a timing chip 41 and a processing chip 42 connected to each other, the timing chip 41 is connected with the first laser emitter 1, the second laser emitter 2 and the laser detector 3 respectively, and the processing chip 42 Connect with the first laser emitter 1 and the second laser emitter 2.
  • the processing chip 42 sends the above-mentioned first electrical trigger signal to the timing chip 41 and the first laser emitter 1 respectively, and the timing chip 41 takes the time when the first electrical trigger signal is received as the above-mentioned first time.
  • the processing chip 42 sends the second electrical trigger signal to the timing chip 41 and the second laser emitter 2 respectively, and the timing chip 41 takes the moment when the second electrical trigger signal is received as the second moment.
  • the laser detector 3 obtains an electrical signal through photoelectric conversion, it sends the electrical signal to the timing chip 41, and the timing chip 41 determines the moment when the amplitude of the rising edge of the electrical signal reaches a certain amplitude as receiving the target echo moment.
  • the timing chip 41 sends the first time, the second time and the time when the target echo is received to the processing chip 42, so that the processing chip 42 determines the distance to the target object.
  • the lidar also includes an optical assembly 5 that can rotate in the horizontal direction, and the optical assembly 5 is used to change the propagation direction of the first laser pulse and the second laser pulse (only in Figure 5 The first laser pulse is shown, the second laser pulse is not shown), so that the first laser pulse and the second laser pulse can be irradiated to multiple positions on the target object to realize scanning in the horizontal direction.
  • the optical component 5 is an optical rotating mirror.
  • the optical component 5 is also used to change the propagation direction of the first echo and the second echo, so that the laser detector 3 receives the first echo and the second echo.
  • the horizontal viewing angle can be formed by scanning in the horizontal direction, and the horizontal viewing angle includes N sub-viewing angles, for example, N is a positive integer not less than 2.
  • the number of sub-field angles included in the horizontal field of view ie N
  • horizontal resolution also known as lateral resolution
  • the minimum angle that the lidar can recognize in the horizontal direction is (horizontal field of view/ N).
  • the horizontal field of view and horizontal resolution are described below by taking the first laser pulse as an example.
  • a direction is selected as a 0° (unit: degree) direction based on the optical component 5 , and the 0° direction will not change with the rotation of the optical component 5 .
  • the first laser pulse 1 is emitted to the optical assembly 5, and the first laser pulse 1' reflected by the optical assembly 5 is irradiated to the position 1 on the target object, and the first laser pulse 1
  • the angle between ' and 0° is angle 1.
  • the optical assembly 5 is rotated once, and the first laser pulse 2 is emitted to the optical assembly 5, and the first laser pulse 2' reflected by the rotated optical assembly 5 is irradiated to the position 2 on the target object.
  • the angle between a laser pulse 2' and 0° is angle 2
  • the angle between angle 2 and angle 1 is a sub-field angle.
  • the target distance from the target object determined by the chip 4 in the above description refers to the distance from a position on the target object. That is to say, during the process of determining the target distance to the target object, the optical assembly 5 is fixed and will not rotate.
  • the target distance from the target object determined by the chip 4 is also called an effective distance-measuring point.
  • a point cloud image of the target object can be obtained through one scan in the horizontal direction, and one scan refers to a 360° scan of the target object in the horizontal direction.
  • the point cloud image includes a plurality of valid ranging points, and each valid ranging point is used to indicate a distance from a position on the target object.
  • the pointing angle of the first laser emitter 1 is fixed, therefore, the included angles between each first laser pulse emitted to the optical component 5 and 0° are the same.
  • the pointing angle of the second laser emitter 2 is also fixed, which will not be repeated here.
  • the pointing angle of the first laser emitter 1 is different from that of the second laser emitter 2 . In other words, there is an included angle between the pointing angle of the first laser emitter 1 and the pointing angle of the second laser emitter 2 that is not 0°.
  • the purpose of making the pointing angle of the first laser emitter 1 different from that of the second laser emitter 2 is to enable the first laser pulse and the second laser pulse to irradiate to the same position on the target object with a certain time difference .
  • the certain time difference is the time difference between the first moment when the first laser pulse is emitted and the second moment when the second laser pulse is emitted.
  • the first laser pulse emitted by the first laser emitter 1 to the optical component 5 is reflected to the position A on the target object.
  • the optical assembly 5 has rotated compared to moment t4 , so the first laser pulse emitted by the first laser emitter 1 to the optical assembly 5 is reflected to the removal position of the target object Location B other than A.
  • the second laser pulse emitted by the second laser emitter 2 to the optical assembly 5 will also be reflected to the position B on the target object , without being reflected to position A on the target object. Therefore, as shown in FIG. 7 , it is necessary to make the pointing angle of the first laser emitter 1 different from that of the second laser emitter 2, so that the second laser pulse can be reflected to the position on the target object at time t4 a.
  • the first laser pulse and the second laser pulse can be irradiated on the target object under a certain time difference (t 4 -t 3 , that is, the time difference between the above-mentioned first moment and the second moment).
  • the relationship between the above-mentioned time difference and the angle of the pointing angle refers to the following formula (2), and the angle of the pointing angle is the difference between the pointing angle of the first laser emitter 1 and the pointing angle of the second laser emitter 2 Angle between:
  • ⁇ T is the time difference between the first moment and the second moment
  • ⁇ is the angle between the pointing angles
  • f is the scanning frequency of the lidar.
  • the scan frequency is used to indicate the number of scans that can be completed per second. According to the above description, completing one scan refers to scanning the target object at 360° in the horizontal direction.
  • the first laser pulse and the second laser pulse need to be emitted to the same position on the optical component 5 . Since the pointing angle of the first laser emitter 1 is different from that of the second laser emitter 2, the first laser emitter 1 and the second laser emitter 2 need to be arranged at different positions of the laser radar. Therefore, the first The laser transmitter 1 and the second laser transmitter 2 have different optical paths. Correspondingly, the laser detector 3 will receive the first echo and the second echo at different positions. As shown in FIG. 8 , FIG. 8 shows a schematic diagram of a laser detector 3 receiving the first echo and the second echo, and the laser detector 3 includes a plurality of detection units.
  • an embodiment of the present application provides a method for measuring distance.
  • the method can be applied to a laser radar chip, or to a processing chip included in the chip. As shown in Fig. 9, the method includes the following steps 901-903.
  • the first moment is earlier than the second moment.
  • the energy of the first laser pulse is different from the energy of the second laser pulse.
  • the distance measurement range of the lidar provided in the embodiment of the present application is: the union of the first ranging range and the second ranging range. Since the first ranging range is related to the energy of the first laser pulse, the second ranging range is related to the energy of the second laser pulse, and the energy of the first laser pulse is different from the energy of the second laser pulse, the first ranging The range is also different from the second ranging range, so that the union of the first ranging range and the second ranging range is larger than both the first ranging range and the second ranging range. Therefore, the embodiment of the present application expands the distance measurement range of the lidar and improves the applicability. Furthermore, the pulse width of the first laser pulse is the same as or different from the pulse width of the second laser pulse.
  • the energy of the first laser pulse is greater than the energy of the second laser pulse, or the energy of the first laser pulse is smaller than the energy of the second laser pulse. In some embodiments, the energy of the first laser pulse is greater than the energy of the second laser pulse. Since the energy of the first laser pulse is greater than the energy of the second laser pulse, the ranging blind area of the first laser pulse is larger than the ranging blind area of the second laser pulse.
  • the embodiment of the present application adds the second laser pulse on the basis of the first laser pulse, so that the ranging blind area of the lidar is changed from the ranging blind area of the first laser pulse to The ranging blind zone of the second laser pulse reduces the ranging blind zone of the lidar, thereby further improving the applicability of the lidar.
  • the first laser pulse and the second laser pulse are selected according to the ranging blind zone threshold and the measurement distance threshold, and the ranging blind zone threshold and the measuring distance threshold are determined according to actual requirements.
  • the laser pulse with higher energy among the first laser pulse and the second laser pulse is used to provide the measurement distance threshold
  • the laser pulse with smaller energy is used to provide the ranging blind zone threshold.
  • the upper limit of the first ranging range is 200m
  • the second laser pulse with a ranging blind zone of 0-0.5m and the upper limit of the second ranging range of 10m the energy ratio of the second laser pulse to the first laser pulse is 1/20
  • the second laser pulse and the first laser pulse can be referred to in FIG. 10 .
  • the time difference between the first moment and the second moment is determined based on at least one of the scanning frequency of the laser radar and the included angle of the pointing angle, and the included angle of the pointing angle is the pointing angle of the first laser emitter angle and the pointing angle of the second laser emitter.
  • the time difference is determined based on the scanning frequency of the lidar. For example, a first correspondence between the time difference and the scanning frequency may be set, so that the first correspondence is queried based on the scanning frequency to obtain the time difference corresponding to the scanning frequency. In some other implementation manners, the time difference is determined based on the included angle of pointing angles. For example, a second corresponding relationship between the time difference and the included pointing angle can be set, so that the second corresponding relationship can be queried based on the included pointing angle to obtain the time difference corresponding to the included pointing angle. In some other implementations, the time difference is determined based on the scanning frequency of the lidar and the included angle of the pointing angle. For this implementation, refer to the description corresponding to the above formula (2), and details will not be repeated here.
  • the time difference is smaller than the upper limit of the time difference
  • the upper limit of the time difference is the difference between the light emitting period of the first laser pulse and the pulse width of the first laser pulse.
  • the light-emitting period of the first laser pulse is determined based on at least one of the scanning frequency of the laser radar, the horizontal field of view angle of the laser radar, and the horizontal resolution of the laser radar.
  • the light-emitting period of the first laser pulse is determined based on the scanning frequency of the laser radar, the horizontal field of view of the laser radar, and the horizontal resolution of the laser radar.
  • the light-emitting period of a laser pulse is according to the following formula (3 )Sure:
  • T is the light-emitting period of the first laser pulse
  • f is the scanning frequency of the lidar
  • ⁇ is the horizontal field of view of the lidar
  • x is the horizontal resolution of the lidar.
  • the time difference is greater than the lower limit of the time difference, which is the pulse width of the first laser pulse, the recovery time of the laser detector, and the time required to measure the upper limit of the first ranging range
  • Maximum, maximum distance is the maximum distance that can be measured based on the energy of the first laser pulse.
  • the reason why the time difference needs to be greater than the pulse width of the first laser pulse is that after receiving the first echo, the second echo is received at least at intervals of the pulse width of the first laser pulse, so that the laser detector can Distinguish between the first echo and the second echo.
  • the reason why the time difference needs to be greater than the recovery time of the laser detector is that the laser detector cannot perform photoelectric conversion within the recovery time, so after receiving the first echo, it is necessary to wait for the laser detector to recover before allowing the laser detector to receive the second echo, to ensure that the photoelectric conversion can be normally performed on the second echo after receiving the second echo.
  • the reason why the time difference needs to be greater than the time required to measure the upper limit of the first ranging range is that the upper limit of the first ranging range is also the maximum distance that the laser radar can measure.
  • the first laser pulse and the second The flight time of one echo is the longest, and the time to receive the first echo is the latest. Therefore, it is necessary to ensure that the second echo can be received after receiving the first echo even when the first echo is received at the latest. Echo, to avoid the change of the receiving order of the first echo and the second echo, which will affect the subsequent distance measurement.
  • the target echo includes at least one of the first echo and the second echo
  • the first echo is the echo formed by the target object reflecting the first laser pulse
  • the second echo is the target object reflecting the second laser Echoes formed by pulses.
  • the photoelectric conversion method of the laser detector after receiving the target echo can refer to the description corresponding to FIG. 2 above, and will not be repeated here.
  • the target moment includes at least one moment among the first moment and the second moment.
  • the target moment matches the target echo. That is to say, which kind of echo is included in the target echo, the target time includes the emission time of the laser pulse used to form the echo.
  • the target echo comprises a first echo and a second echo
  • the target instant comprises a first instant and a second instant. If the target echo is the first echo, the target moment is the first moment. If the target echo is the second echo, the target moment is the second moment.
  • determining the target distance to the target object based on the time when the target echo is received and the target time includes: determining the reference distance to the target object according to the time when the target echo is received and the target time distance. A target distance to the target object is determined based on the reference distance to the target object.
  • the manner of determining the reference distance to the target object includes the following three situations.
  • the target echo includes the first echo and the second echo
  • the target time includes the first moment and the second moment
  • both the first echo and the second echo can be received.
  • the first distance threshold is the lower limit of the first ranging range
  • the second distance threshold is the upper limit of the second ranging range.
  • the received first echo and second echo can be seen in Figure 12, the first echo is not submerged by the first clutter of the first laser pulse, and the second echo is not submerged by the second clutter of the second laser pulse Submerged so that the laser detector can receive and distinguish between the first echo and the second echo.
  • the pulse width of the first clutter is greater than that of the second clutter, and the maximum amplitude of the first echo is greater than that of the second echo. value.
  • the laser detector needs to be set at time t5 , and the time period between the first time moment and time t5 is used as the time period for receiving the first clutter, and the time period between time t5 and the second time The time period between is used as the time period for receiving the first echo. Therefore, the laser detector ignores the time period between the first moment and the t5 moment, and regards the echo received in the time period between the t5 moment and the second moment as the first echo, thereby distinguishing the first Clutter and first echo.
  • the laser detector also needs to set time t6 , use the time period between the second time moment and time t6 as the time period for receiving the second clutter, and use the time period between time t6 and the next emission of the first laser
  • the time period between the instants of the pulses is used as a time period for receiving the second echo, so as to distinguish the second clutter from the second echo, which will not be repeated here.
  • determining the reference distance to the target object according to the moment when the target echo is received and the target moment includes: determining the first distance according to the moment when the first echo is received and the first moment, and determining the first distance according to the moment when the first echo is received The time of the second echo and the second time determine the second distance.
  • a reference distance to the target object is determined according to the first distance and the second distance.
  • the first distance and the second distance are determined according to the above formula (1).
  • one of the first distance and the second distance may be selected as the reference distance to the target object.
  • the first distance is used as the reference distance to the target object.
  • weighted summation of the first distance and the second distance may also be performed to obtain a reference distance to the target object. In the process of weighted summation, the weights corresponding to the first distance and the second distance are the same or different.
  • determining the target distance to the target object based on the reference distance to the target object includes: detecting a first sub-moment when the amplitude of the rising edge of the first echo reaches the reference amplitude, And the second sub-moment when the amplitude of the rising edge of the second echo reaches the reference amplitude.
  • the difference between the first sub-time and the second sub-time is determined as the correction index value, and the correction information is queried to obtain the distance compensation value corresponding to the correction index value.
  • determining the distance compensation value is to reduce the influence brought by the timing error.
  • the moment when the first laser pulse is emitted is recorded as the first moment
  • the moment when the second laser pulse is emitted is recorded as the second moment. Since the first laser emitter emits the first laser pulse according to the first electrical trigger signal, the moment when the first electrical trigger signal is sent can be recorded as the moment when the first laser pulse is emitted, and the error at the first moment is often smaller, Same for the second moment. Therefore, the above-mentioned timing error is mainly caused by the target echo.
  • the moment when the amplitude of the rising edge of the electrical signal reaches a certain amplitude is determined as the moment when the target echo is received.
  • the target echo is formed by the reflection of the target object, so the waveform of the target echo is affected by the distance, surface shape, reflectivity and other factors of the target object.
  • the rising edge of the waveform is not stable enough, and the amplitude of the rising edge of the waveform reaches The moment of a certain amplitude is also different, thus forming a timing error. For example, referring to Fig. 3, if the rising edge of the target echo is smaller than the slope in Fig.
  • the moment when the amplitude of the rising edge of the target echo reaches a certain amplitude is later than the t2 moment shown in Fig. 3, Then the determined time of receiving the target echo is also later than the time t2 shown in FIG. 3 .
  • the time when the target echo is received should be the time corresponding to the starting point of the rising edge shown in FIG. 3 , which should be earlier than the time t2 shown in FIG. 3 . It can be seen that the determined time of receiving the target echo is different from the time of ideally receiving the target echo, which forms a timing error.
  • the time when the target echo is received needs to be used. Due to the existence of the above-mentioned timing error, the time when the target echo is received is not accurate enough, thus affecting the accuracy of distance measurement. Therefore, after the reference distance to the target object is determined based on the time when the target echo is received, the reference distance needs to be compensated by the distance compensation value to obtain the target distance to the target object. In this way, the influence brought by the above-mentioned timing error can be reduced, and the accuracy of the measured distance (that is, the target distance to the target object) can be ensured.
  • the distance compensation value corresponds to the calibration index value, and only the rising edges of the first echo and the second echo need to be measured in the process of determining the calibration index value, without measuring the first echo or the second echo the falling edge of the wave.
  • a relatively accurate correction index value can still be determined in case 1, so that an accurate distance compensation value can be obtained, thereby ensuring the accuracy of the measured target distance.
  • FIG. 13 shows that when the distance between the first distance threshold and the second distance threshold is small, the waveform of the first echo is a saturated waveform.
  • the second echo is shifted forward in the time domain by the time difference between the first moment and the second moment, so that the rising edges of the first echo and the second echo coincide.
  • the first sub-moment t 7 is determined based on the rising edge of the first echo
  • the second sub-moment t 8 is determined based on the rising edge of the second echo, so that the correction index value (t 8 -t 7 ).
  • FIG. 14 shows that when the distance between the first distance threshold and the second distance threshold is relatively large, the waveform of the first echo is an unsaturated waveform. Then the rising edges of the first echo and the second echo coincide.
  • the first sub-moment t 9 is determined based on the rising edge of the first echo
  • the second sub-moment t 10 is determined based on the rising edge of the second echo, so that the correction index value (t 10 -t 9 ).
  • the energy of the second echo decreases, and the amplitude and pulse width of the second echo decrease, so that (t 10 -t 9 )>(t 8 -t 7 ).
  • the second echoes shown in Figure 13 and Figure 14 are the second echoes that have moved forward in the direction of the abscissa, and the forward distance is the time difference between the first moment and the second moment value.
  • the second echo may not be moved forward, so as to obtain the above correction index value.
  • the correction information is queried to obtain the distance compensation value, and the correction information includes the correspondence between the correction index value and the distance compensation value.
  • the correction information includes but not limited to a correction table or a correction function.
  • the distance compensation value obtained by query is positive or negative. After the query obtains the distance compensation value, the distance compensation value and the reference distance to the target object are summed to obtain the target distance to the target object.
  • the above correction table or correction function is obtained through a calibration process.
  • multiple calibration distances are determined between the first distance threshold and the second distance threshold.
  • the calibration distance is also called the true distance, which can be measured by other devices with higher precision than the laser radar.
  • the distance value measured by the laser radar and the above-mentioned correction index value are determined, and the correction index value is determined based on the rising edge of the first echo and the rising edge of the second echo received by the laser radar.
  • the distance compensation value between the distance value measured by the lidar and the calibration distance is determined. If it is necessary to obtain a correction table, the corresponding relationship between the distance compensation value and the correction index value constitutes a correction table. If it is necessary to obtain a correction function, it is fitted according to the distance compensation value and the correction index value.
  • the target echo is the first echo
  • the target time is the first time
  • the second distance threshold is the upper limit of the second ranging range
  • the third distance threshold is the upper limit of the first ranging range.
  • the received first echo can be seen in Figure 15.
  • the first echo is not submerged by the first clutter of the first laser pulse, while the second echo cannot be received because of the long distance, so the laser detector can only receive the first echo. an echo.
  • the laser detector distinguishes the first clutter and the first echo, refer to the description in the above case 1, which will not be repeated here.
  • determining the reference distance to the target object according to the moment when the target echo is received and the target moment includes: determining the reference distance to the target object according to the moment when the first echo is received and the first moment .
  • the reference distance is determined according to the above formula (1), wherein the difference between the moment when the first echo is received and the first moment is ⁇ t in the above formula (1).
  • determining the target distance to the target object based on the reference distance to the target object includes: detecting the third sub-moment when the rising edge of the first echo reaches the reference amplitude, and detecting the first The falling edge of the echo reaches the fourth sub-moment of the reference amplitude.
  • the difference between the third sub-time and the fourth sub-time is determined as the correction index value, and the correction information is queried to obtain the distance compensation value corresponding to the correction index value. Determine the target distance to the target object according to the reference distance and the distance compensation value.
  • the target echo is the second echo
  • the target moment is the second moment
  • the first distance threshold is the lower limit of the first ranging range
  • the fourth distance threshold is based on the lower limit of the second ranging range.
  • the received second echo can be seen in Figure 16, the first echo is submerged by the first clutter of the first laser pulse, and the second echo is not submerged by the second clutter of the second laser pulse, so the laser The detector can receive the second echo.
  • determining the reference distance to the target object according to the time when the target echo is received and the target time includes: determining the reference distance to the target object according to the time when the second echo is received and the second time .
  • the reference distance is determined according to the above formula (1), wherein the difference between the time when the second echo is received and the second time is ⁇ t in the above formula (1).
  • determining the target distance to the target object based on the reference distance to the target object includes: detecting the fifth sub-moment when the rising edge of the second echo reaches the reference amplitude, and detecting the second The falling edge of the echo reaches the sixth sub-moment of the reference amplitude.
  • the difference between the fifth sub-time and the sixth sub-time is determined as the correction index value, and the correction information is queried to obtain the distance compensation value corresponding to the correction index value. Determine the target distance to the target object according to the reference distance and the distance compensation value.
  • the above three situations are all situations where the energy of the first laser pulse is greater than the energy of the second laser pulse.
  • the principle is the same as that of the above three cases, and will not be repeated here.
  • the energy of the two laser pulses emitted by the two laser emitters included in the laser radar is different, so the ranging ranges corresponding to the two laser pulses are also different. Since the ranging range of the lidar is the union of the ranging ranges corresponding to the two laser pulses, the distance measuring range of the lidar is expanded and the applicability of the lidar is improved.
  • An embodiment of the present application provides a device for measuring distance, which is applied to a chip included in a laser radar, and the laser radar further includes a first laser emitter, a second laser emitter, and a laser detector connected to the chip.
  • the device includes:
  • a control module 1701 configured to control the first laser emitter to emit a first laser pulse at the first moment for the target object, and control the second laser emitter to emit the second laser pulse at the second moment for the target object, the first moment is earlier than the first At a second moment, the energy of the first laser pulse is different from the energy of the second laser pulse, the first laser pulse corresponds to the first ranging range, and the second laser pulse corresponds to the second ranging range;
  • the control module 1701 is also used to control the laser detector to receive the target echo;
  • a determining module 1702 configured to determine the target distance to the target object based on the time when the target echo is received and the target time, the target distance is located in the union of the first ranging range and the second ranging range, and the target echo Including at least one of the first echo and the second echo, the first echo is the echo formed by the target object reflecting the first laser pulse, and the second echo is the echo formed by the target object reflecting the second laser pulse , the target moment includes at least one of the first moment and the second moment.
  • the determination module 1702 is configured to determine the reference distance to the target object based on the time when the target echo is received and the target time; and determine the distance to the target object based on the reference distance to the target object. target distance between.
  • the target echo includes a first echo and a second echo
  • the target moment includes a first moment and a second moment
  • the determining module 1702 is configured to, according to the moment when the first echo is received and the first The first distance is determined at a time
  • the second distance is determined according to the time when the second echo is received and the second time
  • the reference distance to the target object is determined according to the first distance and the second distance
  • the reference distance is greater than the first distance threshold and Less than the second distance threshold
  • the first distance threshold is based on the lower limit of the first ranging range
  • the second distance threshold is the upper limit of the second ranging range
  • the energy of the first laser pulse is greater than the energy of the second laser pulse.
  • the determination module 1702 is configured to detect the first sub-moment when the amplitude of the rising edge of the first echo reaches the reference amplitude, and the amplitude of the rising edge of the second echo reaches the reference amplitude
  • the second sub-moment determine the difference between the first sub-moment and the second sub-moment as the correction index value, query the correction information to obtain the distance compensation value corresponding to the correction index value; according to the reference distance and the distance compensation value, determine the distance from the target Target distance between objects.
  • the target echo is the first echo
  • the target time is the first time
  • the determination module 1702 is configured to determine the reference with the target object according to the time when the first echo is received and the first time distance, the reference distance is greater than the second distance threshold and less than the third distance threshold, the second distance threshold is the upper limit of the second ranging range, the third distance threshold is the upper limit of the first ranging range, and the energy of the first laser pulse is greater than the first The energy of the second laser pulse.
  • the target echo is the second echo
  • the target time is the second time
  • the determining module 1702 is configured to determine the reference with the target object according to the time when the second echo is received and the second time Distance, the reference distance is greater than the fourth distance threshold and less than the first distance threshold, the first distance threshold is the lower limit of the first ranging range, the fourth distance threshold is based on the lower limit of the second ranging range, and the energy of the first laser pulse is greater than Energy of the second laser pulse.
  • the time difference between the first moment and the second moment is determined based on at least one of the scanning frequency of the laser radar and the included angle of the pointing angle, and the included angle of the pointing angle is the pointing angle of the first laser emitter angle and the pointing angle of the second laser emitter.
  • the time difference is smaller than the upper limit of the time difference
  • the upper limit of the time difference is the difference between the light emitting period of the first laser pulse and the pulse width of the first laser pulse
  • the light emitting period of the first laser pulse is based on the laser radar At least one of the scanning frequency, the horizontal field of view of the laser radar, and the horizontal resolution of the laser radar is determined.
  • the time difference is greater than the lower limit of the time difference, which is the pulse width of the first laser pulse, the recovery time of the laser detector, and the time required to measure the upper limit of the first ranging range maximum value.
  • the energy of the two laser pulses emitted by the two laser emitters included in the laser radar is different, so the ranging ranges corresponding to the two laser pulses are also different. Since the ranging range of the lidar is the union of the ranging ranges corresponding to the two laser pulses, the distance measuring range of the lidar is extended and the applicability of the lidar is improved.
  • the program can be stored in a computer-readable storage medium.
  • the above-mentioned The storage medium mentioned may be a read-only memory, a magnetic disk or an optical disk, and the like.

Abstract

测量距离的方法及激光雷达，属于激光探测技术领域。测量距离的方法应用于激光雷达包括的芯片（4），激光雷达还包括与芯片（4）连接的第一激光发射器（1）、第二激光发射器（2）和激光探测器（3）。测量距离的方法包括：控制第一激光发射器（1）在第一时刻针对目标对象发射第一激光脉冲，控制第二激光发射器（2）在第二时刻针对目标对象发射第二激光脉冲（901）；控制激光探测器（3）接收目标回波（902）；基于接收到目标回波的时刻和目标时刻确定与目标对象之间的目标距离。其中，目标距离位于第一激光脉冲对应的第一测距范围与第二激光脉冲对应的第二测距范围的并集之中（903）。测量距离的方法扩大了激光雷达的距离测量范围，提高了激光雷达的适用性。

Description

测量距离的方法及激光雷达
本申请要求于2021年12月23日提交的申请号为202111593148.7、申请名称为“测量距离的方法及激光雷达”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及激光探测技术领域，特别涉及一种测量距离的方法及激光雷达。
背景技术
随着激光探测技术的发展，激光探测技术的应用场景也越来越多，对距离进行测量属于其中一种的应用场景。其中，用于对距离进行测量的设备包括激光雷达(Laser Radar)，按照激光雷达所发射的激光类型进行分类，可以将激光雷达分为脉冲式激光雷达、连续式激光雷达等等。
相关技术基于脉冲式激光雷达提供了一种TOF(Time of Flight，飞行时间)法。在TOF法中，脉冲式激光雷达发射激光脉冲，激光脉冲被待测量的对象反射产生回波，脉冲式激光雷达接收回波。之后，计算回波的接收时间和激光脉冲的发射时间之间的差值，得到激光脉冲的飞行时间。根据飞行时间和激光脉冲的飞行速度，即可计算得到对象的距离。
然而，相关技术提供的方法存在一定的测距盲区。其原因在于，激光脉冲发射的激光脉冲除了被待测量的对象反射产生回波之外，还会被激光雷达本身的内外结构反射产生杂波。并且，杂波的能量大于回波的能量。因此，如果激光雷达在接收杂波的过程中又接收到了回波，则激光雷达接收的回波会被能量更大的杂波所淹没，或者说，激光雷达不能识别接收的回波。由此，导致了激光雷达不能确定回波的接收时间，也就不能计算得到对象的距离，从而形成了测距盲区。正是由于相关技术提供的方法存在一定的测距盲区，因而限缩了距离测量范围，适用性不强。
发明内容
本申请实施例提供了一种测量距离的方法及激光雷达，以解决相关技术提供的方法限缩了距离测量范围、适用性不强的问题。所述技术方案如下：
一方面，提供了一种测量距离的方法，方法应用于激光雷达包括的芯片，激光雷达还包括与芯片连接的第一激光发射器、第二激光发射器和激光探测器，方法包括：
控制第一激光发射器在第一时刻针对目标对象发射第一激光脉冲，控制第二激光发射器在第二时刻针对目标对象发射第二激光脉冲，第一时刻早于第二时刻，第一激光脉冲的能量与第二激光脉冲的能量不同，第一激光脉冲对应第一测距范围，第二激光脉冲对应第二测距范围；
控制激光探测器接收目标回波，基于接收到目标回波的时刻和目标时刻确定与目标对象之间的目标距离，目标距离位于第一测距范围与第二测距范围的并集之中，目标回波包括第一回波和第二回波中的至少一个回波，第一回波为目标对象反射第一激光脉冲形成的回波，第二回波为目标对象反射第二激光脉冲形成的回波，目标时刻包括第一时刻和第二时刻中的 至少一个时刻。
在示例性实施例中，基于接收到目标回波的时刻和目标时刻确定与目标对象之间的目标距离，包括：根据接收到目标回波的时刻和目标时刻，确定与目标对象之间的参考距离；基于与目标对象之间的参考距离，确定与目标对象之间的目标距离。
在示例性实施例中，目标回波包括第一回波和第二回波，目标时刻包括第一时刻和第二时刻，根据接收到目标回波的时刻和目标时刻，确定与目标对象之间的参考距离，包括：根据接收到第一回波的时刻和第一时刻确定第一距离，根据接收到第二回波的时刻和第二时刻确定第二距离；根据第一距离和第二距离确定与目标对象之间的参考距离，参考距离大于第一距离阈值且小于第二距离阈值，第一距离阈值为基于第一测距范围的下限，第二距离阈值为第二测距范围的上限，第一激光脉冲的能量大于第二激光脉冲的能量。
在示例性实施例中，基于与目标对象之间的参考距离，确定与目标对象之间的目标距离，包括：检测第一回波的上升沿的幅值达到参考幅值的第一子时刻，以及第二回波的上升沿的幅值达到参考幅值的第二子时刻；将第一子时刻和第二子时刻之间的差值确定为校正指标值，查询校正信息得到校正指标值对应的距离补偿值；根据参考距离和距离补偿值，确定与目标对象之间的目标距离。
在示例性实施例中，目标回波为第一回波，目标时刻为第一时刻，根据接收到目标回波的时刻和目标时刻，确定与目标对象之间的参考距离，包括：根据接收到第一回波的时刻和第一时刻确定与目标对象之间的参考距离，参考距离大于第二距离阈值且小于第三距离阈值，第二距离阈值为第二测距范围的上限，第三距离阈值为第一测距范围的上限，第一激光脉冲的能量大于第二激光脉冲的能量。
在示例性实施例中，目标回波为第二回波，目标时刻为第二时刻，根据接收到目标回波的时刻和目标时刻，确定与目标对象之间的参考距离，包括：根据接收到第二回波的时刻和第二时刻确定与目标对象之间的参考距离，参考距离大于第四距离阈值且小于第一距离阈值，第一距离阈值为第一测距范围的下限，第四距离阈值为基于第二测距范围的下限，第一激光脉冲的能量大于第二激光脉冲的能量。
在示例性实施例中，第一时刻与第二时刻之间的时刻差值基于激光雷达的扫描频率和指向角夹角中的至少一种确定，指向角夹角为第一激光发射器的指向角与第二激光发射器的指向角之间的夹角。
在示例性实施例中，时刻差值小于时刻差值上限，时刻差值上限为第一激光脉冲的发光周期与第一激光脉冲的脉宽之差，第一激光脉冲的发光周期基于激光雷达的扫描频率、激光雷达的水平视场角和激光雷达的水平分辨率中的至少一种确定。
在示例性实施例中，时刻差值大于时刻差值下限，时刻差值下限为第一激光脉冲的脉宽、激光探测器的恢复时间和测量第一测距范围的上限所需的时间中的最大值。
一方面，提供了一种激光雷达，激光雷达包括第一激光发射器、第二激光发射器、激光探测器和芯片，第一激光发射器、第二激光发射器、激光探测器分别与芯片连接，芯片用于执行本申请任一示例性实施例提供的量距离的方法。
一方面，提供了一种测量距离的装置，该装置应用于激光雷达包括的芯片，激光雷达还包括与芯片连接的第一激光发射器、第二激光发射器和激光探测器，装置包括：
控制模块，用于控制第一激光发射器在第一时刻针对目标对象发射第一激光脉冲，控制 第二激光发射器在第二时刻针对目标对象发射第二激光脉冲，第一时刻早于第二时刻，第一激光脉冲的能量与第二激光脉冲的能量不同，第一激光脉冲对应第一测距范围，第二激光脉冲对应第二测距范围；
控制模块，还用于控制激光探测器接收目标回波；
确定模块，用于基于接收到目标回波的时刻和目标时刻确定与目标对象之间的目标距离，目标距离位于第一测距范围与第二测距范围的并集之中，目标回波包括第一回波和第二回波中的至少一个回波，第一回波为目标对象反射第一激光脉冲形成的回波，第二回波为目标对象反射第二激光脉冲形成的回波，目标时刻包括第一时刻和第二时刻中的至少一个时刻。
在示例性实施例中，确定模块，用于根据接收到目标回波的时刻和目标时刻，确定与目标对象之间的参考距离；基于与目标对象之间的参考距离，确定与目标对象之间的目标距离。
在示例性实施例中，目标回波包括第一回波和第二回波，目标时刻包括第一时刻和第二时刻，确定模块，用于根据接收到第一回波的时刻和第一时刻确定第一距离，根据接收到第二回波的时刻和第二时刻确定第二距离；根据第一距离和第二距离确定与目标对象之间的参考距离，参考距离大于第一距离阈值且小于第二距离阈值，第一距离阈值为基于第一测距范围的下限，第二距离阈值为第二测距范围的上限，第一激光脉冲的能量大于第二激光脉冲的能量。
在示例性实施例中，确定模块，用于检测第一回波的上升沿的幅值达到参考幅值的第一子时刻，以及第二回波的上升沿的幅值达到参考幅值的第二子时刻；将第一子时刻和第二子时刻之间的差值确定为校正指标值，查询校正信息得到校正指标值对应的距离补偿值；根据参考距离和距离补偿值，确定与目标对象之间的目标距离。
在示例性实施例中，目标回波为第一回波，目标时刻为第一时刻，确定模块，用于根据接收到第一回波的时刻和第一时刻确定与目标对象之间的参考距离，参考距离大于第二距离阈值且小于第三距离阈值，第二距离阈值为第二测距范围的上限，第三距离阈值为第一测距范围的上限，第一激光脉冲的能量大于第二激光脉冲的能量。
在示例性实施例中，目标回波为第二回波，目标时刻为第二时刻，确定模块，用于根据接收到第二回波的时刻和第二时刻确定与目标对象之间的参考距离，参考距离大于第四距离阈值且小于第一距离阈值，第一距离阈值为第一测距范围的下限，第四距离阈值为基于第二测距范围的下限，第一激光脉冲的能量大于第二激光脉冲的能量。
在示例性实施例中，第一时刻与第二时刻之间的时刻差值基于激光雷达的扫描频率和指向角夹角中的至少一种确定，指向角夹角为第一激光发射器的指向角与第二激光发射器的指向角之间的夹角。
在示例性实施例中，时刻差值小于时刻差值上限，时刻差值上限为第一激光脉冲的发光周期与第一激光脉冲的脉宽之差，第一激光脉冲的发光周期基于激光雷达的扫描频率、激光雷达的水平视场角和激光雷达的水平分辨率中的至少一种确定。
在示例性实施例中，时刻差值大于时刻差值下限，时刻差值下限为第一激光脉冲的脉宽、激光探测器的恢复时间和测量第一测距范围的上限所需的时间中的最大值。
本申请实施例所提供的技术方案带来的有益效果至少包括：
本申请实施例中激光雷达包括的两个激光发射器发射的两个激光脉冲的能量不同，因而两个激光脉冲对应的测距范围也不同。由于激光雷达的测距范围是两个激光脉冲对应的测距 范围的并集，因而扩展了激光雷达的距离测量范围，提高了激光雷达的适用性。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本申请实施例提供的一种杂波及回波的示意图；
图2是本申请实施例提供的一种激光雷达的结构示意图；
图3是本申请实施例提供的一种光电转换得到的电信号的示意图；
图4是本申请实施例提供的一种激光雷达的结构示意图；
图5是本申请实施例提供的一种光学组件的结构示意图；
图6是本申请实施例提供的一种水平视场角的示意图；
图7是本申请实施例提供的一种第一激光脉冲和第二激光脉冲照射至同一位置的示意图；
图8是本申请实施例提供的一种激光探测器接收第一回波和第二回波的示意图；
图9是本申请实施例提供的一种测量距离的方法的流程图；
图10是本申请实施例提供的一种第一激光脉冲和第二激光脉冲的示意图；
图11是本申请实施例提供的一种不同情况下的目标回波的示意图；
图12是本申请实施例提供的一种目标回波的示意图；
图13是本申请实施例提供的一种确定校正指标值的示意图；
图14是本申请实施例提供的一种确定校正指标值的示意图；
图15是本申请实施例提供的一种目标回波的示意图；
图16是本申请实施例提供的一种目标回波的示意图；
图17是本申请实施例提供的一种测量距离的装置的结构示意图。
具体实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合附图对本申请实施方式作进一步地详细描述。
在激光探测技术领域中，激光雷达是一种用于对距离进行测量的设备，脉冲式激光雷达属于激光雷达的其中一种。基于脉冲式激光雷达，相关技术提供了一种TOF法，该方法根据激光脉冲的飞行时间(也即是传播时间)和飞行速度(也即是传播速度)计算与对象之间的距离。例如，激光雷达针对对象发送激光脉冲的时间为t 0，激光雷达接收回波(由对象反射激光脉冲形成)的时间为t 1，则激光脉冲的飞行时间为Δt＝t 1-t 0，将激光脉冲的飞行速度记为c，则与对象之间的距离按照如下的公式(1)计算：
Figure PCTCN2021141346-appb-000001
然而，该方法存在一定的测距盲区，下面对测距盲区进行说明。
激光雷达针对对象发射激光脉冲之后，除了对象反射激光脉冲形成回波之外，激光雷达的内外结构也会反射该激光脉冲，从而形成杂波，激光雷达会接收到所形成的杂波。由于该杂波的形成位置与激光雷达的距离较近，且激光雷达的内外结构所进行的反射接近于镜面反射，因而该杂波的能量较大，从而使得杂波具有较大的幅值和脉宽。参见图1，图1示出了 一种杂波波形，该杂波波形的积分值表示杂波的能量。并且，该杂波波形是一种饱和波形，由于该杂波实际的最大幅值超出了激光雷达所能接收的最大幅值，因而表现为饱和波形。其中，本申请实施例中脉宽为半高宽，半高宽也即是将幅值的一半处的波形宽度。
对于由对象反射形成的回波，由于回波的形成位置与激光雷达的距离远于上述杂波的形成位置与激光雷达的距离，且对象所进行的反射往往属于漫反射，因而回波的能量较小，小于杂波的能量。参见图1，图1示出了一种回波波形，该回波波形的积分值表示回波的能量。需要说明的是，该回波波形可能是饱和波形，也可能是不饱和波形，图1所示的不饱和波形仅为举例，不用于对回波波形造成限定。无论回波波形如何，如果激光雷达是在接收杂波的过程中接收到了该回波，则该回波均会由于能量小于杂波而被杂波淹没，或者说，激光雷达无法从杂波中识别出该回波。因此，激光雷达无法确定接收回波的时间(即上述t 1)，也就无法确定对象的距离。
根据以上说明可知，在激光雷达接收杂波的过程中，激光雷达无法确定对象的距离，因而激光雷达接收杂波的这段时间对应的距离范围即为测距盲区。由于杂波的形成位置与激光雷达的距离较近，因而激光雷达在发射激光脉冲之后的较短时间内便会接收到杂波，则接收杂波的这段时间对应的距离范围是与激光雷达之间距离较近的范围。也就是说，上述测距盲区往往存在于较近距离上。其中，该测距盲区与激光雷达的内外结构的材料、激光雷达的光功率(光功率影响着激光雷达发射的激光脉冲的能量)和激光雷达的探测增益(探测增益影响着激光雷达接收回波及杂波的灵敏度)等因素有关。
以图1所示的情况为例，接收杂波的持续时间约为30ns(单位：纳秒)。在此基础上，将上述激光脉冲的飞行速度c取值为3·10 8m/s(单位：米/秒)，则可以计算出测距盲区的最大距离l max＝(30·10 -9·3·10 8)/2＝4.5m(单位：米)，因而测距盲区为0-4.5m。
由于上述方法存在一定的测距盲区，因而限缩了距离测量范围，降低了上述方法的适用性。因此，亟待提供一种具备较大的距离测量范围的激光雷达，以及对应的测量距离的方法，参见下文本申请实施例中的说明。
本申请实施例提供了一种激光雷达。参见图2，该激光雷达包括第一激光发射器1、第二激光发射器2、激光探测器3和芯片4，第一激光发射器1、第二激光发射器2、激光探测器3分别与芯片4连接。示例性地，激光探测器3为线阵探测器，例如APD(Avalanche Photo Diode，雪崩光电二极管)等积分式光电探测器。
其中，芯片4向第一激光发射器1发送第一电触发信号，使得第一激光发射器1根据该第一电触发信号，针对需要进行距离测量的目标对象发射第一激光脉冲。并且，芯片4将第一激光发射器1发射第一激光脉冲的时刻记录为第一时刻。芯片4还向第二激光发射器2发送第二电触发信号，使得第二激光发射器2根据该第二电触发信号针对目标对象发射第二激光脉冲，芯片4将第二激光发射器2发射第二激光脉冲的时刻记录为第二时刻。
需要说明的是，上述第一激光脉冲对应一定的距离测量范围，即第一测距范围，第一测距范围与第一激光脉冲的能量有关。第一激光脉冲的能量越大，则第一测距范围的下限越大，第一测距范围的上限也越大。其中，第一测距范围的下限也即是第一激光脉冲对应的测距盲区的最大距离。
如果与目标对象之间的距离位于该第一测距范围内，则激光探测器3能够接收目标对象反射第一激光脉冲形成的第一回波，且能够确定接收到第一回波的时刻。如果与目标对象之 间的距离小于第一测距范围的下限，则第一回波会被第一激光脉冲对应的第一杂波所淹没，激光探测器3即使接收到第一回波，也无法确定接收到第一回波的时刻。如果与目标对象之间的距离大于第一测距范围的上限，则第一激光脉冲可能由于能量不足而无法飞行至目标对象，也就无法形成第一回波，或者，第一激光脉冲已飞行至目标对象，但目标对象反射形成的第一回波由于能量不足而无法飞行至激光探测器3。总之，在与目标对象之间的距离大于第一测距范围的上限的情况下，则激光探测器3无法接收第一回波，也无法确定接收到第一回波的时刻。因此，激光探测器3可能接收到第一回波，也可能无法接收到第一回波。
此外，第二激光发射器2发射的第二激光光束可以被目标对象反射形成第二回波，第二回波也对应有一定的距离测量范围，即第二测距范围，该第二测距范围与第二激光脉冲的能量有关。第二激光脉冲的能量越大，则第二测距范围的下限越大，第二测距范围的上限也越大。其中，第二测距范围的下限也即是第二激光脉冲对应的测距盲区的最大距离。总之，激光探测器3可能接收到第二回波，也可能无法接收到第二回波。
因此，激光探测器3所能接收到的是第一回波和第二回波中的至少一个回波。下文中将该至少一个回波称为目标回波，以便于进行描述。
激光探测器3接收到目标回波之后，对目标回波进行光电转换，得到具有一定波形的电信号。如图3所示，图3示出了一种示例性的电信号，该电信号的横坐标为时间，纵坐标为相对光功率。激光探测器3向芯片4发送转换得到的电信号，芯片4将该电信号的上升沿的幅值达到一定幅值的时刻确定为接收到目标回波的时刻。例如，图3所示的t 2时刻即为接收到目标回波的时刻。
芯片4在确定接收到目标回波的时刻之后，基于接收到目标回波的时刻和目标时刻，确定与目标对象之间的目标距离。其中，目标时刻包括上述第一时刻和第二时刻中的至少一个时刻。芯片4确定与目标对象之间的目标距离的方式参见下文方法实施例中的说明，此处暂不进行赘述。
示例性地，参见图4，芯片4包括相互连接的计时芯片41和处理芯片42，计时芯片41分别与第一激光发射器1、第二激光发射器2和激光探测器3连接，处理芯片42与第一激光发射器1和第二激光发射器2连接。
其中，处理芯片42向计时芯片41和第一激光发射器1分别发送上述第一电触发信号，计时芯片41将接收到第一电触发信号的时刻作为上述第一时刻。处理芯片42向计时芯片41和第二激光发射器2分别发送上述第二电触发信号，计时芯片41将接收到第二电触发信号的时刻作为上述第二时刻。此外，激光探测器3通过光电转换得到电信号之后，向计时芯片41发送该电信号，由计时芯片41将该电信号的上升沿的幅值达到一定幅值的时刻确定为接收到目标回波的时刻。之后，计时芯片41向处理芯片42发送上述第一时刻、第二时刻和接收到目标回波的时刻，从而由处理芯片42确定与目标对象之间的距离。
示例性地，如图5所示，该激光雷达还包括可在水平方向上旋转的光学组件5，该光学组件5用于改变第一激光脉冲和第二激光脉冲的传播方向(图5中仅示出第一激光脉冲，未示出第二激光脉冲)，使得第一激光脉冲和第二激光脉冲可以照射至目标对象上的多个位置，以实现水平方向上的扫描。示例性地，该光学组件5为光学转镜。当然，在目标对象反射形成第一回波和第二回波之后，该光学组件5还用于改变第一回波和第二回波的传播方向，以使得激光探测器3接收第一回波和第二回波。
通过在水平方向上的扫描可以形成水平视场角，该水平视场角包括N个子视场角，例如，N为不小于2的正整数。水平视场角包括的子视场角的数量(即N)称为水平分辨率(又称横向分辨率)，则激光雷达在水平方向上所能识别的最小角度即为(水平视场角/N)。其中，水平分辨率越大，则第一激光脉冲和第二激光脉冲在目标对象上能够照射到的位置越多。下面以第一激光脉冲为例，对水平视场角和水平分辨率进行说明。
首先，参见图6，基于光学组件5选择一个方向作为0°(单位：度)方向，该0°方向不会随着光学组件5的旋转而改变。之后，在光学组件5未旋转的情况下，向光学组件5发射第一激光脉冲1，经光学组件5反射后的第一激光脉冲1’照射至目标对象上的位置1，第一激光脉冲1’与0°之间的夹角为角度1。之后，令该光学组件5旋转1次，并向光学组件5发射第一激光脉冲2，经旋转后的光学组件5反射后的第一激光脉冲2’照射至目标对象上的位置2，该第一激光脉冲2’与0°之间的夹角为角度2，角度2与角度1之间的夹角即为1个子视场角。以此类推，每令光学组件5旋转1次，均向光学组件5发射一次第一激光脉冲，直至第N次令光学组件5旋转1次之后，向光学组件5发射第一激光脉冲N，经光学组件5反射后的第一激光脉冲N’照射至目标对象上的位置N，该第一激光脉冲N’与0°之间的夹角为角度N。其中，角度N与角度1之间的夹角即为水平视场角。由图6可以看出，该水平视场角的原点为光学组件5的旋转轴，光学组件5的旋转轴又称激光雷达的扫描中心。
需要说明的是，上文说明中芯片4确定的与目标对象之间的目标距离，是指与目标对象上的一个位置之间的距离。也就是说，在确定与目标对象之间的目标距离的过程中，光学组件5是固定的，不会发生旋转。芯片4确定的与目标对象之间的目标距离又称为一个有效测距点。其中，通过水平方向上的一次扫描可以得到目标对象的一张点云图，一次扫描是指在水平方向上对目标对象进行360°的扫描。点云图上包括多个有效测距点，每个有效测距点均用于指示与目标对象上的一个位置之间的距离。
在本申请实施例中，第一激光发射器1的指向角是固定的，因此，向光学组件5发射的各个第一激光脉冲与0°之间的夹角均相同。此外，第二激光发射器2的指向角也是固定的，此处不再进行赘述。示例性地，第一激光发射器1的指向角与第二激光发射器2的指向角不同。或者说，第一激光发射器1的指向角与第二激光发射器2的指向角之间具有不为0°的指向角夹角。令第一激光发射器1的指向角与第二激光发射器2的指向角不同的目的在于：使得第一激光脉冲和第二激光脉冲可以在一定的时间差下照射至目标对象上的同一个位置。其中，一定的时间差也即是发射第一激光脉冲的第一时刻与发射第二激光脉冲的第二时刻之间的时刻差值。
参见图7，在t 4时刻(即上述第一时刻)，第一激光发射器1向光学组件5发射的第一激光脉冲被反射至目标对象上的位置A。在t 3时刻(即上述第二时刻)，光学组件5相比于t 4时刻发生了旋转，因而第一激光发射器1向光学组件5发射的第一激光脉冲被反射至目标对象上除位置A之外的位置B。如果第一激光发射器1的指向角与第二激光发射器2的指向角相同，则第二激光发射器2向光学组件5发射的第二激光脉冲也会被反射至目标对象上的位置B，而不会被反射至目标对象上的位置A。因此，如图7所示，需要使得第一激光发射器1的指向角与第二激光发射器2的指向角不同，以使得第二激光脉冲在t 4时刻能够被反射至目标对象上的位置A。由此，便可以使得第一激光脉冲和第二激光脉冲在一定的时间差下(t 4-t 3，也即上述第一时刻与第二时刻之间的时刻差值)照射至目标对象上的同一个位置(位置 A)。
示例性地，上述时间差与指向角夹角之间的关系参见如下的公式(2)，指向角夹角也即是第一激光发射器1的指向角与第二激光发射器2的指向角之间的夹角：
Figure PCTCN2021141346-appb-000002
其中，ΔT为第一时刻与第二时刻之间的时刻差值，α为指向角夹角，f为激光雷达的扫描频率。扫描频率用于指示每秒钟能够完成的扫描次数，根据上文说明可知，完成一次扫描是指在水平方向上对目标对象进行360°的扫描。
以扫描频率f＝20HZ(单位：赫兹)为例，如果指向角夹角α＝3.8′(单位：分，60′＝1°)，则时间差ΔT＝8.7μs(单位：微秒)，如果指向角夹角α＝4.3′，则时间差ΔT＝10μs。
此外，需要说明的是，本申请实施例需要使得第一激光脉冲和第二激光脉冲被发射至光学组件5上的同一位置。由于第一激光发射器1的指向角与第二激光发射器2的指向角不同，因而第一激光发射器1与第二激光发射器2需要设置在激光雷达的不同位置上，因此，第一激光发射器1与第二激光发射器2为不同光路。相应地，激光探测器3会在不同的位置接收到第一回波和第二回波。如图8所示，图8示出了一种激光探测器3接收第一回波和第二回波的示意图，该激光探测器3包括多个探测单元。
基于上述图2、图4和图5所示的激光雷达，参见图9，本申请实施例提供了一种测量距离的方法。该方法可应用于激光雷达的芯片中，或者应用于芯片包括的处理芯片中。如图9所示，该方法包括如下的步骤901-903。
901，控制第一激光发射器在第一时刻针对目标对象发射第一激光脉冲，控制第二激光发射器在第二时刻针对目标对象发射第二激光脉冲，第一激光脉冲对应第一测距范围，第二激光脉冲对应第二测距范围。
其中，第一时刻早于第二时刻。第一激光脉冲的能量与第二激光脉冲的能量不同。相比于仅采用第一激光脉冲或第二激光脉冲的激光雷达，本申请实施例提供的激光雷达的距离测量范围为：第一测距范围和第二测距范围的并集。由于第一测距范围与第一激光脉冲的能量相关，第二测距范围与第二激光脉冲的能量相关，且第一激光脉冲的能量与第二激光脉冲的能量不同，因而第一测距范围与第二测距范围也不同，从而使得第一测距范围与第二测距范围的并集既大于第一测距范围，又大于第二测距范围。因此，本申请实施例扩大了激光雷达的距离测量范围，提高了适用性。此外，第一激光脉冲的脉宽与第二激光脉冲的脉宽相同或不同。
示例性地，第一激光脉冲的能量大于第二激光脉冲的能量，或者，第一激光脉冲的能量小于第二激光脉冲的能量。在一些实施方式中，第一激光脉冲的能量大于第二激光脉冲的能量。由于第一激光脉冲的能量大于第二激光脉冲的能量，因而第一激光脉冲的测距盲区大于第二激光脉冲的测距盲区。相比于仅采用第一激光脉冲的激光雷达，本申请实施例通过在第一激光脉冲的基础上增加第二激光脉冲，使得激光雷达的测距盲区由第一激光脉冲的测距盲区转变为第二激光脉冲的测距盲区，也即是缩小了激光雷达的测距盲区，从而进一步提高了激光雷达的适用性。
示例性地，本申请实施例根据测距盲区阈值和测量距离阈值选择第一激光脉冲和第二激光脉冲，测距盲区阈值和测量距离阈值根据实际需求确定。其中，第一激光脉冲和第二激光脉冲中能量较大的一个激光脉冲用于提供测量距离阈值，而能量较小的一个激光脉冲用于提 供测距盲区阈值。以需要的测距盲区阈值为0.5m，需要的测量距离阈值为200m，且第一激光脉冲的能量大于第二激光脉冲的能量为例，令能量较大的第一激光脉冲提供测量距离阈值200m，令能量较小的第二激光脉冲提供测距盲区阈值0.5m。比如，选择测距盲区为3-5m、第一测距范围的上限为200m的第一激光脉冲，以及测距盲区为0-0.5m、第二测距范围的上限为10m的第二激光脉冲。此种情况下，第二激光脉冲与第一激光脉冲的能量比为1/20，第二激光脉冲和第一激光脉冲可以参见图10。
在示例性实施例中，第一时刻与第二时刻之间的时刻差值基于激光雷达的扫描频率和指向角夹角中的至少一种确定，指向角夹角为第一激光发射器的指向角与第二激光发射器的指向角之间的夹角。
在一些实施方式中，时刻差值基于激光雷达的扫描频率确定。例如，可以设置时刻差值与扫描频率之间的第一对应关系，从而基于扫描频率查询该第一对应关系，得到扫描频率对应的时刻差值。在另一些实施方式中，时刻差值基于指向角夹角确定。例如可以设置时刻差值与指向角夹角之间的第二对应关系，从而基于指向角夹角查询该第二对应关系，得到指向角夹角对应的时刻差值。在再一些实施方式中，时刻差值基于激光雷达的扫描频率和指向角夹角确定，本实施方式参见上文公式(2)对应的说明，此处不再进行赘述。
在示例性实施例中，时刻差值小于时刻差值上限，时刻差值上限为第一激光脉冲的发光周期和第一激光脉冲的脉宽之差。时刻差值需要小于时刻差值上限的原因在于：需要使得第一激光脉冲与第二激光脉冲一一对应。
其中，第一激光脉冲的发光周期基于激光雷达的扫描频率、激光雷达的水平视场角和激光雷达的水平分辨率中的至少一种确定。示例性地，第一激光脉冲的发光周期基于激光雷达的扫描频率、激光雷达的水平视场角和激光雷达的水平分辨率确定，此种情况下一激光脉冲的发光周期按照如下的公式(3)确定：
Figure PCTCN2021141346-appb-000003
在公式(3)中，T为第一激光脉冲的发光周期，f为激光雷达的扫描频率，β为激光雷达的水平视场角，x为激光雷达的水平分辨率。以f＝20HZ、β＝120°且x＝960为例，则第一激光脉冲的发光周期T＝17.36μs。
在示例性实施例中，时刻差值大于时刻差值下限，时刻差值下限为第一激光脉冲的脉宽、激光探测器的恢复时间和测量第一测距范围的上限所需的时间中的最大值，最大距离为基于第一激光脉冲的能量所能测量的最大距离。
其中，时刻差值需要大于第一激光脉冲的脉宽的原因在于：在接收到第一回波之后，至少间隔第一激光脉冲的脉宽再接收到第二回波，以使得激光探测器可以区分第一回波与第二回波。时刻差值需要大于激光探测器的恢复时间的原因在于：激光探测器在恢复时间内无法进行光电转换，因而在接收到第一回波之后，需要等待激光探测器恢复之后再使得激光探测器接收第二回波，以保证接收第二回波之后可以正常对第二回波进行光电转换。时刻差值需要大于测量第一测距范围的上限所需的时间的原因在于：第一测距范围的上限也即是激光雷达所能测量的最大距离，此种情况下第一激光脉冲和第一回波的飞行时间最长，接收到第一回波的时间最晚，因而需要保证在最晚接收到第一回波的情况下，也能在接收到第一回波之后再接收第二回波，避免第一回波和第二回波的接收顺序发生改变，影响后续的距离测量。
902，控制激光探测器接收目标回波。
其中，目标回波包括第一回波和第二回波中的至少一个回波，第一回波为目标对象反射第一激光脉冲形成的回波，第二回波为目标对象反射第二激光脉冲形成的回波。其中，激光探测器接收目标回波之后进行光电转换的方式参见上文图2对应的说明，此处不再进行赘述。
903，基于接收到目标回波的时刻和目标时刻确定与目标对象之间的目标距离，目标距离位于第一测距范围与第二测距范围的并集之中。
其中，目标时刻包括第一时刻和第二时刻中的至少一个时刻。示例性地，本申请实施例中目标时刻与目标回波相匹配。也就是说，目标回波中包括哪种回波，则目标时刻中包括用于形成该回波的激光脉冲的发射时刻。因此，如果目标回波包括第一回波和第二回波，则目标时刻包括第一时刻和第二时刻。如果目标回波为第一回波，则目标时刻为第一时刻。如果目标回波为第二回波，则目标时刻为第二时刻。
在示例性实施例中，基于接收到目标回波的时刻和目标时刻确定与目标对象之间的目标距离，包括：根据接收到目标回波的时刻和目标时刻，确定与目标对象之间的参考距离。基于与目标对象之间的参考距离，确定与目标对象之间的目标距离。
其中，在第一激光脉冲的能量大于第二激光脉冲的能量的情况下，确定与目标对象之间的参考距离的方式包括如下的三种情况。
情况一，目标回波包括第一回波和第二回波，目标时刻包括第一时刻和第二时刻。
参见图11，在与目标对象之间的参考距离大于第一距离阈值且小于第二距离阈值的情况下，既能接收到第一回波，又能接收到第二回波。其中，第一距离阈值为第一测距范围的下限，第二距离阈值为第二测距范围的上限。所接收的第一回波和第二回波可以参见图12，第一回波未被第一激光脉冲的第一杂波淹没，第二回波也未被第二激光脉冲的第二杂波淹没，因而激光探测器可以接收并区分第一回波和第二回波。并且，由于第一激光脉冲的能量大于第二激光脉冲的能量，因而第一杂波的脉宽大于第二杂波的脉宽，第一回波的最大幅值大于第二回波的最大幅值。
如图12所示，激光探测器需要设置t 5时刻，将第一时刻与t 5时刻之间的时间段作为用于接收第一杂波的时间段，且将t 5时刻与第二时刻之间的时间段作为用于接收第一回波的时间段。因此，激光探测器会忽略第一时刻与t 5时刻之间的时间段，而将t 5时刻与第二时刻之间的时间段接收到的回波作为第一回波，从而区分了第一杂波和第一回波。相应地，激光探测器还需要设置t 6时刻，将第二时刻与t 6时刻之间的时间段作为用于接收第二杂波的时间段，且将t 6时刻与下一次发射第一激光脉冲的时刻之间的时间段作为用于接收第二回波的时间段，从而区分第二杂波与第二回波，此处不再进行赘述。
示例性地，根据接收到目标回波的时刻和目标时刻，确定与目标对象之间的参考距离，包括：根据接收到第一回波的时刻和第一时刻确定第一距离，根据接收到第二回波的时刻和第二时刻确定第二距离。根据第一距离和第二距离确定与目标对象之间的参考距离。其中，本申请实施例按照上文公式(1)确定第一距离和第二距离。在确定第一距离时，接收到第一回波的时刻与第一时刻之间的差值即为上文公式(1)中的Δt。在确定第二距离时，接收到第二回波的时刻与第二时刻之间的差值即为上文公式(1)中的Δt。
示例性地，本申请实施例可以从第一距离和第二距离中任选其一作为与目标对象之间的参考距离。例如，本申请实施例将第一距离作为与目标对象之间的参考距离。或者，本申请实施例也可以对第一距离和第二距离进行加权求和，得到与目标对象之间的参考距离。在加 权求和的过程中，第一距离和第二距离对应的权重相同或不同。
在示例性实施例中，基于与目标对象之间的参考距离，确定与目标对象之间的目标距离，包括：检测第一回波的上升沿的幅值达到参考幅值的第一子时刻，以及第二回波的上升沿的幅值达到参考幅值的第二子时刻。将第一子时刻和第二子时刻之间的差值确定为校正指标值，查询校正信息得到校正指标值对应的距离补偿值。根据参考距离和距离补偿值，确定与目标对象之间的目标距离。
其中，确定距离补偿值是为了减小计时误差带来的影响。如前所述，本申请实施例将发射第一激光脉冲的时刻记录为第一时刻，将发射第二激光脉冲的时刻记录为第二时刻。由于第一激光发射器根据第一电触发信号发射第一激光脉冲，因而可以将发送第一电触发信号的时刻记录作为上述发射第一激光脉冲的时刻，则第一时刻的误差往往较小，第二时刻同理。因此，上述计时误差主要由目标回波引起。
如前所述，激光探测器对目标回波进行光电转换得到电信号后，将该电信号的上升沿的幅值达到一定幅值的时刻确定为接收到目标回波的时刻。然而，目标回波由目标对象反射形成，因而该目标回波的波形受目标对象的距离、面型、反射率等因素的影响，波形的上升沿不够稳定，则波形的上升沿的幅值达到一定幅值的时刻也不同，从而形成计时误差。例如，参见图3，如果目标回波的上升沿相比于图3的斜率更小，则目标回波的上升沿的幅值达到一定幅值的时刻晚于图3所示的t 2时刻，则确定出的接收到目标回波的时刻也晚于图3所示的t 2时刻。但在理想情况下，接收到目标回波的时刻应为图3所示的上升沿的起点处对应的时刻，该时刻应为早于图3所示的t 2时刻。可见，确定出的接收到目标回波的时刻与理想情况下接收到目标回波的时刻不同，形成了计时误差。
根据上文公式(1)对应的说明可知，在测量距离的过程中，需要使用到接收到目标回波的时刻。由于上述计时误差的存在，导致接收到目标回波的时刻不够准确，因而影响了距离测量的准确率。因此，在基于接收到目标回波的时刻确定与目标对象之间的参考距离之后，还需要通过距离补偿值对参考距离进行补偿，得到与目标对象之间的目标距离。由此，能够减小上述计时误差带来的影响，保证了所测量的距离(即与目标对象之间的目标距离)的准确性。
在情况一中，距离补偿值与校正指标值相对应，在确定校正指标值的过程中仅需测量第一回波和第二回波的上升沿，而无需测量第一回波或第二回波的下降沿。在由于震荡、噪声、临近波形叠加等问题导致下降沿被淹没或产生错误的下降沿的情况下，情况一仍能确定出较为准确的校正指标值，从而可以得到准确的距离补偿值，进而保证了所测量的目标距离的准确性。
参见图13，图13示出了在第一距离阈值与第二距离阈值之间，距离较小的情况下，第一回波的波形呈饱和波形的情况。将第二回波在时间域上向前平移第一时刻与第二时刻之间的时刻差值，则第一回波和第二回波的上升沿重合。在达到参考幅值的情况下，基于第一回波的上升沿确定第一子时刻t 7，基于第二回波的上升沿确定第二子时刻t 8，从而得到校正指标值为(t 8-t 7)。
参见图14，图14示出了在第一距离阈值与第二距离阈值之间，距离较大的情况下，第一回波的波形呈不饱和波形的情况。则第一回波和第二回波的上升沿重合。在达到参考幅值的情况下，基于第一回波的上升沿确定第一子时刻t 9，基于第二回波的上升沿确定第二子时 刻t 10，从而得到校正指标值为(t 10-t 9)。需要说明的是，由于距离有所提升，因而第二回波的能量减小，第二回波的幅值和脉宽均减小，从而使得(t 10-t 9)＞(t 8-t 7)。
需要说明的是，图13和图14所示的第二回波均为在横坐标方向上已前移过的第二回波，前移距离为第一时刻与第二时刻之间的时刻差值。本申请实施例中，也可以不对第二回波进行前移，从而得到上述校正指标值。
在得到校正指标值之后，查询校正信息得到距离补偿值，校正信息包括校正指标值和距离补偿值之间的对应关系。示例性地，校正信息包括但不限于校正表或者校正函数。另外，查询得到的距离补偿值为正数或负数。在查询得到距离补偿值之后，对距离补偿值和与目标对象之间的参考距离进行求和，从而得到与目标对象之间的目标距离。
需要说明的是，上述校正表或者校正函数通过标定过程得到。在标定过程中，在第一距离阈值和第二距离阈值之间确定多个标定距离，标定距离又称距离真值，可以通过比激光雷达精度更高的其他设备测量得到。在每个标定距离处，确定激光雷达测量的距离值以及上述校正指标值，该校正指标值基于激光雷达接收的第一回波的上升沿和第二回波的上升沿确定。之后，再确定激光雷达测量的距离值和标定距离之间的距离补偿值。如果需要获得校正表，则将距离补偿值与校正指标值的对应关系组成校正表。如果需要获得校正函数，则根据距离补偿值与校正指标值进行拟合。
情况二，目标回波为第一回波，目标时刻为第一时刻。
参见图11，在与目标对象之间的参考距离大于第二距离阈值且小于第三距离阈值的情况下，仅能接收到第一回波。其中，第二距离阈值为第二测距范围的上限，第三距离阈值为第一测距范围的上限。所接收的第一回波可以参见图15，第一回波未被第一激光脉冲的第一杂波淹没，而第二回波则因为距离较远无法接收，因而激光探测器仅能接收第一回波。激光探测器区分第一杂波和第一回波的方式参见上文情况一中的说明，此处不再进行赘述。
示例性地，根据接收到目标回波的时刻和目标时刻，确定与目标对象之间的参考距离，包括：根据接收到第一回波的时刻和第一时刻确定与目标对象之间的参考距离。本申请实施例按照上文公式(1)确定该参考距离，其中，接收到第一回波的时刻与第一时刻之间的差值即为上文公式(1)中的Δt。
在示例性实施例中，基于与目标对象之间的参考距离，确定与目标对象之间的目标距离，包括：检测第一回波的上升沿达到参考幅值的第三子时刻，检测第一回波的下降沿达到参考幅值的第四子时刻。将第三子时刻和第四子时刻之间的差值确定为校正指标值，查询校正信息得到校正指标值对应的距离补偿值。根据参考距离和距离补偿值，确定与目标对象之间的目标距离。
在情况二中，由于仅能获取第一回波，因而需要检测第一回波的上升沿和下降沿，得到上述校正指标值。在得到校正指标值之后，查询距离补偿值，以及，基于参考距离和距离补偿值确定目标距离的方式参见上文情况一中的说明，此处不再进行赘述。
情况三，目标回波为第二回波，目标时刻为第二时刻。
其中，参见图11，在与目标对象之间的参考距离大于第四距离阈值且小于第一距离阈值的情况下，仅能接收到第二回波。其中，第一距离阈值为第一测距范围的下限，第四距离阈值为基于第二测距范围的下限。所接收的第二回波可以参见图16，第一回波被第一激光脉冲的第一杂波所淹没，第二回波则未被第二激光脉冲的第二杂波所淹没，因而激光探测器可以 接收第二回波。激光探测器区分第二杂波和第二回波的方式参见上文情况一中的说明，此处不再进行赘述。
示例性地，根据接收到目标回波的时刻和目标时刻，确定与目标对象之间的参考距离，包括：根据接收到第二回波的时刻和第二时刻确定与目标对象之间的参考距离。本申请实施例按照上文公式(1)确定该参考距离，其中，接收到第二回波的时刻与第二时刻之间的差值即为上文公式(1)中的Δt。
在示例性实施例中，基于与目标对象之间的参考距离，确定与目标对象之间的目标距离，包括：检测第二回波的上升沿达到参考幅值的第五子时刻，检测第二回波的下降沿达到参考幅值的第六子时刻。将第五子时刻和第六子时刻之间的差值确定为校正指标值，查询校正信息得到校正指标值对应的距离补偿值。根据参考距离和距离补偿值，确定与目标对象之间的目标距离。
在情况三中，由于仅能获取第二回波，因而需要检测第二回波的上升沿和下降沿，从而得到上述校正指标值。在得到校正指标值之后，查询距离补偿值，以及，基于参考距离和距离补偿值确定目标距离的方式参见上文情况一中的说明，此处不再进行赘述。
此外，以上三种情况均为第一激光脉冲的能量大于第二激光脉冲的能量的情况。对于第一激光脉冲的能量小于第二激光脉冲的能量的情况，与以上三种情况原理相同，此处不再进行赘述。
综上所述，本申请实施例中激光雷达包括的两个激光发射器发射的两个激光脉冲的能量不同，因而两个激光脉冲对应的测距范围也不同。由于激光雷达的测距范围是两个激光脉冲对应的测距范围的并集，因而扩大了激光雷达的距离测量范围，提高了激光雷达的适用性。
本申请实施例提供了一种测量距离的装置，该装置应用于激光雷达包括的芯片，激光雷达还包括与芯片连接的第一激光发射器、第二激光发射器和激光探测器。参见图17，该装置包括：
控制模块1701，用于控制第一激光发射器在第一时刻针对目标对象发射第一激光脉冲，控制第二激光发射器在第二时刻针对目标对象发射第二激光脉冲，第一时刻早于第二时刻，第一激光脉冲的能量与第二激光脉冲的能量不同，第一激光脉冲对应第一测距范围，第二激光脉冲对应第二测距范围；
控制模块1701，还用于控制激光探测器接收目标回波；
确定模块1702，用于基于接收到目标回波的时刻和目标时刻确定与目标对象之间的目标距离，目标距离位于第一测距范围与第二测距范围的并集之中，目标回波包括第一回波和第二回波中的至少一个回波，第一回波为目标对象反射第一激光脉冲形成的回波，第二回波为目标对象反射第二激光脉冲形成的回波，目标时刻包括第一时刻和第二时刻中的至少一个时刻。
在示例性实施例中，确定模块1702，用于根据接收到目标回波的时刻和目标时刻，确定与目标对象之间的参考距离；基于与目标对象之间的参考距离，确定与目标对象之间的目标距离。
在示例性实施例中，目标回波包括第一回波和第二回波，目标时刻包括第一时刻和第二时刻，确定模块1702，用于根据接收到第一回波的时刻和第一时刻确定第一距离，根据接收到第二回波的时刻和第二时刻确定第二距离；根据第一距离和第二距离确定与目标对象之间 的参考距离，参考距离大于第一距离阈值且小于第二距离阈值，第一距离阈值为基于第一测距范围的下限，第二距离阈值为第二测距范围的上限，第一激光脉冲的能量大于第二激光脉冲的能量。
在示例性实施例中，确定模块1702，用于检测第一回波的上升沿的幅值达到参考幅值的第一子时刻，以及第二回波的上升沿的幅值达到参考幅值的第二子时刻；将第一子时刻和第二子时刻之间的差值确定为校正指标值，查询校正信息得到校正指标值对应的距离补偿值；根据参考距离和距离补偿值，确定与目标对象之间的目标距离。
在示例性实施例中，目标回波为第一回波，目标时刻为第一时刻，确定模块1702，用于根据接收到第一回波的时刻和第一时刻确定与目标对象之间的参考距离，参考距离大于第二距离阈值且小于第三距离阈值，第二距离阈值为第二测距范围的上限，第三距离阈值为第一测距范围的上限，第一激光脉冲的能量大于第二激光脉冲的能量。
在示例性实施例中，目标回波为第二回波，目标时刻为第二时刻，确定模块1702，用于根据接收到第二回波的时刻和第二时刻确定与目标对象之间的参考距离，参考距离大于第四距离阈值且小于第一距离阈值，第一距离阈值为第一测距范围的下限，第四距离阈值为基于第二测距范围的下限，第一激光脉冲的能量大于第二激光脉冲的能量。
在示例性实施例中，第一时刻与第二时刻之间的时刻差值基于激光雷达的扫描频率和指向角夹角中的至少一种确定，指向角夹角为第一激光发射器的指向角与第二激光发射器的指向角之间的夹角。
在示例性实施例中，时刻差值小于时刻差值上限，时刻差值上限为第一激光脉冲的发光周期与第一激光脉冲的脉宽之差，第一激光脉冲的发光周期基于激光雷达的扫描频率、激光雷达的水平视场角和激光雷达的水平分辨率中的至少一种确定。
在示例性实施例中，时刻差值大于时刻差值下限，时刻差值下限为第一激光脉冲的脉宽、激光探测器的恢复时间和测量第一测距范围的上限所需的时间中的最大值。
综上所述，本申请实施例中激光雷达包括的两个激光发射器发射的两个激光脉冲的能量不同，因而两个激光脉冲对应的测距范围也不同。由于激光雷达的测距范围是两个激光脉冲对应的测距范围的并集，因而扩展了激光雷达的距离测量范围，提高了激光雷达的适用性。
需要说明的是，上述图17提供的装置在实现其功能时，仅以上述各功能模块的划分进行举例说明，实际应用中，可以根据需要而将上述功能分配由不同的功能模块完成，即将设备的内部结构划分成不同的功能模块，以完成以上描述的全部或者部分功能。另外，上述实施例提供的装置与方法实施例属于同一构思，其具体实现过程详见方法实施例，这里不再赘述。
上述所有可选技术方案，可以采用任意结合形成本申请的可选实施例，在此不再一一赘述。
本领域普通技术人员可以理解实现上述实施例的全部或部分步骤可以通过硬件来完成，也可以通过程序来指令相关的硬件完成，所述的程序可以存储于一种计算机可读存储介质中，上述提到的存储介质可以是只读存储器，磁盘或光盘等。
以上所述仅为本申请的实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (10)

  1. 一种测量距离的方法，其特征在于，所述方法应用于激光雷达包括的芯片，所述激光雷达还包括与所述芯片连接的第一激光发射器、第二激光发射器和激光探测器，所述方法包括：
    控制所述第一激光发射器在第一时刻针对目标对象发射第一激光脉冲，控制所述第二激光发射器在第二时刻针对所述目标对象发射第二激光脉冲，所述第一时刻早于所述第二时刻，所述第一激光脉冲的能量与所述第二激光脉冲的能量不同，所述第一激光脉冲对应第一测距范围，所述第二激光脉冲对应第二测距范围；
    控制所述激光探测器接收目标回波，基于接收到所述目标回波的时刻和目标时刻确定与所述目标对象之间的目标距离，所述目标距离位于所述第一测距范围与所述第二测距范围的并集之中，所述目标回波包括第一回波和第二回波中的至少一个回波，所述第一回波为所述目标对象反射所述第一激光脉冲形成的回波，所述第二回波为所述目标对象反射所述第二激光脉冲形成的回波，所述目标时刻包括所述第一时刻和所述第二时刻中的至少一个时刻。
  2. 根据权利要求1所述的方法，其特征在于，所述基于接收到所述目标回波的时刻和目标时刻确定与所述目标对象之间的目标距离，包括：
    根据所述接收到所述目标回波的时刻和所述目标时刻，确定与所述目标对象之间的参考距离；
    基于所述与所述目标对象之间的参考距离，确定所述与所述目标对象之间的目标距离。
  3. 根据权利要求2所述的方法，其特征在于，所述目标回波包括所述第一回波和所述第二回波，所述目标时刻包括所述第一时刻和所述第二时刻，所述根据所述接收到所述目标回波的时刻和所述目标时刻，确定与所述目标对象之间的参考距离，包括：
    根据接收到所述第一回波的时刻和所述第一时刻确定第一距离，根据接收到所述第二回波的时刻和所述第二时刻确定第二距离；
    根据所述第一距离和所述第二距离确定所述与所述目标对象之间的参考距离，所述参考距离大于第一距离阈值且小于第二距离阈值，所述第一距离阈值为基于所述第一测距范围的下限，所述第二距离阈值为所述第二测距范围的上限，所述第一激光脉冲的能量大于所述第二激光脉冲的能量。
  4. 根据权利要求3所述的方法，其特征在于，所述基于所述与所述目标对象之间的参考距离，确定所述与所述目标对象之间的目标距离，包括：
    检测所述第一回波的上升沿的幅值达到参考幅值的第一子时刻，以及所述第二回波的上升沿的幅值达到所述参考幅值的第二子时刻；
    将所述第一子时刻和所述第二子时刻之间的差值确定为校正指标值，查询校正信息得到所述校正指标值对应的距离补偿值；
    根据所述参考距离和所述距离补偿值，确定所述与所述目标对象之间的目标距离。
  5. 根据权利要求2所述的方法，其特征在于，所述目标回波为所述第一回波，所述目标 时刻为所述第一时刻，所述根据所述接收到所述目标回波的时刻和所述目标时刻，确定与所述目标对象之间的参考距离，包括：
    根据接收到所述第一回波的时刻和所述第一时刻确定所述与所述目标对象之间的参考距离，所述参考距离大于第二距离阈值且小于第三距离阈值，所述第二距离阈值为所述第二测距范围的上限，所述第三距离阈值为所述第一测距范围的上限，所述第一激光脉冲的能量大于所述第二激光脉冲的能量。
  6. 根据权利要求2所述的方法，其特征在于，所述目标回波为所述第二回波，所述目标时刻为所述第二时刻，所述根据所述接收到所述目标回波的时刻和所述目标时刻，确定与所述目标对象之间的参考距离，包括：
    根据接收到所述第二回波的时刻和所述第二时刻确定所述与所述目标对象之间的参考距离，所述参考距离大于第四距离阈值且小于第一距离阈值，所述第一距离阈值为所述第一测距范围的下限，所述第四距离阈值为基于所述第二测距范围的下限，所述第一激光脉冲的能量大于所述第二激光脉冲的能量。
  7. 根据权利要求1-6任一所述的方法，其特征在于，所述第一时刻与所述第二时刻之间的时刻差值基于所述激光雷达的扫描频率和指向角夹角中的至少一种确定，所述指向角夹角为所述第一激光发射器的指向角与所述第二激光发射器的指向角之间的夹角。
  8. 根据权利要求7所述的方法，其特征在于，所述时刻差值小于时刻差值上限，所述时刻差值上限为第一激光脉冲的发光周期与第一激光脉冲的脉宽之差，所述第一激光脉冲的发光周期基于所述激光雷达的扫描频率、所述激光雷达的水平视场角和所述激光雷达的水平分辨率中的至少一种确定。
  9. 根据权利要求7所述的方法，其特征在于，所述时刻差值大于时刻差值下限，所述时刻差值下限为第一激光脉冲的脉宽、所述激光探测器的恢复时间和测量所述第一测距范围的上限所需的时间中的最大值。
  10. 一种激光雷达，其特征在于，所述激光雷达包括第一激光发射器、第二激光发射器、激光探测器和芯片，所述第一激光发射器、所述第二激光发射器、所述激光探测器分别与所述芯片连接，所述芯片用于执行权利要求1-9任一所述的测量距离的方法。
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